Testing Machine Research Articles

Influence of dental bleaching on the microhardness and flexural strength of resin composites

Purpose. This study aimed to examine the influence of dental bleaching systems (home bleaching system and two in-office bleaching systems) on the surface microhardness, and flexural strength of the two resin composite restorative materials (Beautifil II and OliREVO). Methods. For each test, a total of 48 samples were prepared with both types of composites. The samples of each type of composite were divided at random into four groups each of six samples, control group (C) was not bleached and kept in distilled water, other three groups (G1, G2, and G3) were bleached with 10% hydrogen peroxide (HP) home beaching, 35% and 40% HP in-office bleaching systems, respectively. To measure the composite resin's microhardness, a Vickers microhardness tester was used, while a universal testing machine was used to measure its flexural strength. Results. For statistical analysis, Duncan and ANOVA tests were used. A p-value ≤0.01 indicates statistically significant results. In-office bleaching systems (35% and 40% HP) significantly reduced microhardness and flexural strength of the used resin composites. Generally, the hardness and flexural strength of Beautifil II were better than OliREVO composite. Conclusion. Regarding the physical properties of composite resins, the microhardness and flexural strength may be compromised by bleaching treatments.

Electrification of a Mini Traction Machine and Initial Test Results

Electric vehicles (EVs) continue to evolve, and sales continue to increase as the world pushes toward improved sustainability. This drives the need for research to understand the unique environments in which fluids operate within the Electric Drive Units (EDUs) of EVs in order to improve durability and reduce frictional losses. However, for this to happen, test rigs are required to operate with an electric current passing across the test parts and through the lubricant. Very few electrified test rigs currently exist, with most being adaptations of rigs undertaken by academia and independent and national research labs. In this work, the PCS Mini Traction Machine (MTM) was modified to supply a voltage across a tribological contact. New parts for the MTM were designed in collaboration with the instrument manufacturer. Work was undertaken in both the author’s labs and the manufacturer’s labs with the aim of bringing a commercially available unit to market as quickly as possible. A test matrix was completed on the MTM utilizing a range of temperatures, loads, and voltage inputs for three different lubricants commonly used in EDUs. The test matrix consisted of 36 test conditions, with some runs performed in triplicate, resulting in 81 tests for each oil and a total matrix of 243 tests. The test matrix was run to obtain the results and to test the robustness of the rig design. After testing was completed, the MTM disc wear scars were measured. The results from these measurements indicate that the application of alternating current (AC) and direct current (DC) causes a significant increase in the wear scar compared to non-electrified test conditions. This, in turn, results in increased traction values under non-electrified conditions. It was also noted that the repeatability of the traction curves and end-of-test wear was reduced under both AC and DC electrified conditions.

선삭 가공 공정에서 절삭력에 미치는 영향에 대한 실험계획법을 이용한 가공성 평가

The exorbitant costs in turning manufacturing can be reduced by moderating the costs added to manpower and processes. There has been an increasing trend of relying on numerous machining tests, based on the field experience of the operator, to obtain optimal cutting conditions. As the automobile-parts sector advances, flexible changes in the cutting conditions are required in industrial settings. This study presents an effective method for obtaining the optimal cutting conditions using the Taguchi method, which is the most commonly used experimental design method. The optimal cutting conditions were obtained by formulating a cutting plan based on a minimal experimental design. Furthermore, the average value of the S/N ratio in the Taguchi method was calculated to derive the predicted values of the cutting force and surface roughness for the turning process conditions.

Optimization of Machining Parameters for Nimonic PE16 Using Machine Learning Models

Machining high-temperature alloys such as Nimonic PE16 demands precise control of machining parameters to achieve desired outcomes while minimizing tool wear and optimizing surface finish. In this study, we propose using machine learning regression models combined with synthetic data and response surface methodology strategies to optimize machining parameters for PE16. We aim to develop a predictive model that accurately estimates optimal cutting speeds and feed rates based on key output parameters, including cutting forces and surface roughness. Our methodology involves collecting experimental data from controlled machining tests conducted on PE16 samples under varying conditions. We used the datasets to train and validate regression models to establish correlations between input parameters and machining outcomes. The performance of each model is evaluated based on metrics such as mean absolute error and coefficient of determination. These metrics show relationships within the data and can determine a model’s success. The proposed machine learning framework offers a data-driven approach to optimize machining processes for PE16, facilitating enhanced efficiency, productivity, and quality in nuclear and other high-performance applications. Our findings contribute to understanding machining dynamics in challenging materials and provide valuable insights for intelligent machining systems.

Evaluation of Etching Time Effect on Shear Bond Strength of Orthodontic Brackets Bonded with Self-Adhesive Composite: An in-Vitro Study

Introduction: Precise acid etching of the tooth surface is a significant factor in the strength of the bracket bond. The current study aimed to determine the effect of different application times of acid etching on the shear bond strength of metallic orthodontic brackets under controlled laboratory conditions. Methods: Sixty intact premolar teeth were selected for this in-vitro study. The samples were divided into four groups based on the different acid etching times: 20, 25, 30, and 35 seconds. The teeth surfaces were etched with 37% phosphoric acid according to the specified times, and brackets were bonded to the enamel surface using GC Ortho connect composite. Shear bond strength values of the brackets was measured using a Universal Testing Machine. The amount of Adhesive Remnant Index was also observed using a stereomicroscope. Additionally, the surface roughness of the tooth enamel after bracket bonding was examined using SEM. The results related to shear bond strength were analyzed with one-way ANOVA statistical test and using SPSS version 16 software. The non-parametric Kruskal Wallis (Wallis-Kruskal) test was also used to check the frequency of ARI index. Results: The highest shear bond strength was observed at 25 seconds, and the lowest at 30 seconds. However, there was no significant difference in the shear bond strength of brackets was observed among the four groups (p=0.186). The highest ARI score was observed at 35 seconds, and the lowest at 20 seconds. No statistically significant difference was observed in the ARI scores in different groups. SEM images revealed that the enamel surface porosity was highest at 20 seconds. Conclusion: The results indicate that the shear bond strength and ARI at different acid etching times do not significantly differ. Therefore, orthodontic bracket bonding can be performed with less acid etching time.

Influence of Ageing Treatment on Microstructure and Mechanical Properties of GH4169 Alloy Prepared Using Wire Arc Additive Manufacturing

The effects of solid-solution and ageing treatments on the microstructure and mechanical properties of a GH4169 alloy made by wire arc additive manufacturing, micro-casting, and forging were researched. The microstructure, along with the size and type of precipitated phase, were analysed using an optical microscope, scanning electron microscope, and transmission electron microscope. The strength and toughness were tested using a tensile testing machine. The results show that a polygonal austenite microstructure was obtained for the GH4169 alloy prepared through wire arc additive manufacturing, micro-casting, and forging, followed by solid-solution and double-ageing treatments at different times. There were a few twins in the austenite matrix. A large number of nano-sized γ″- and γ′-precipitated phases and a small number of Laves phases and MX phases were found in the matrix. The tensile strength and yield strength of the GH4169 alloy increased first and then decreased with the ageing time. After ageing for 16 h, the maximum yield strength was 1287 ± 22 MPa, the maximum tensile strength was 1447 ± 19 MPa, and the elongation was about 19.5%. The main strength mechanism is precipitated phase strength and solid-solution strength. The fracture exhibited obvious ductile fracture characteristics.

Titanium oxide and chitosan nanoparticles loaded in methylene blue activated by photodynamic therapy on caries affected dentin disinfection, bond strength, and smear layer removal efficacy

AimEffect of nanoparticles (NPs) loaded methylene blue (MB) mediated photodynamic therapy (PDT) on caries-affected dentin (CAD) against S.mutans, smear layer (SL) elimination, and shear bond strength (SBS) of single bottle 7th generation adhesive. MethodologySixty human molars with carious lesions were selected. Samples were randomly allocated into four groups, based on the disinfection regime (n = 11) Group 1-(CHX), Group 2-(MB-PDT), Group 3-(MB-CNPs-PDT), and Group 4-(MB-TiO2NPs-PDT). Following disinfection S.mutans' survival rate was assessed using the pour plate method. Five specimens from each disinfection group were subjected to SL removal assessment using a scanning electron microscope (SEM). Bonding of 7th generation adhesive and composite restoration was performed on ten samples from each group. Artificial aging of the bonded samples was performed followed by SBS and failure mode analysis using a universal testing machine and stereomicroscope respectively. One-way analysis of variance (ANOVA) and Tukey post hoc test were used to analyze the data. ResultsGroup 3 (MB-CNPs-PDT) treated CAD surface unveiled the lowest survival rate (0.12 ± 0.02 CFU/mL) of tested bacteria, maximum SL removal (1.21 ± 0.35), and highest bond strength (13.42 ± 1.05). However, Group 1 (CHX) treated specimens displayed the highest survival rate (0.53 ± 0.11 CFU/mL) with the lowest SL removal (2.24 ± 0.30) and SBS (8.88 ± 0.73 MPa). ConclusionMB-CNPs-PDT appears to be a suitable alternative to CHX for CAD disinfection as it displayed better antibacterial efficacy, SL removal, and SBS with 7th generation single bottle adhesive.

Does enamel deproteinisation with 10% papain affect shear bond strength of orthodontic adhesives: a randomised controlled trial.

To evaluate the effect of 10% papain as an enamel deproteinising agent on the shear bond strength (SBS) of three orthodontic adhesives: Transbond XT, resin-modified glass ionomer cement (RMGIC) and Biofix. Single-centre, double-blinded, split-mouth randomised controlled trial. Department of Orthodontics and Dentofacial Orthopaedics, Nair Hospital Dental College, Mumbai, India. A total of 20 participants requiring bilateral premolar extraction for fixed orthodontic treatment in both the maxillary and mandibular arches were included in this study. In total, 80 premolars from the above-mentioned participants were divided into four groups as follows: group A: Transbond XT deproteinised with 10% papain gel; group B: Biofix deproteinised with 10% papain gel; group C: RMGIC deproteinised with 10% papain gel; and group D: Transbond XT without enamel deproteinisation as a control group-bonded as instructed by the manufacturer. After deproteinisation, brackets were bonded and after a follow-up period of 28 days, the teeth were extracted. The SBS was then measured using the Universal Testing Machine. The force needed to shear the bracket was documented, and bond strengths were subsequently calculated in megapascals (MPa). The obtained results were subjected to statistical analysis and one-way ANOVA was performed to compare the mean SBS between the groups. Subsequently, pairwise comparisons were conducted using Tukey's post hoc test. There was a statistically significant difference in SBS among all groups (P = 0.002). The SBS of TransXT with deproteinisation increased significantly compared with TransXT without deproteinisation (P = 0.03). There was no statistically significant difference between the SBS of TransXT without deproteinisation and RMGIC (P = 0.47) and Biofix (P = 0.39), both with deproteinisation. The use of 10% papain for deproteinising enamel improved the SBS of all materials. Deproteinising improved the SBS of RMGIC and Biofix to the level of TransXT without deproteinisation.

Novel Mn and Si alloyed complex phase steel for automotive applications

Automotive industries require materials with higher strength, plasticity and crashworthiness, aiming for 3rd generation of advanced high strength steels (AHSS) with medium Mn, Si and minor alloying elements. In this investigation, 3rd generation AHSS were synthesized using a vacuum arc melting furnace with manganese (Mn) and silicon (Si) as major alloying elements as well as minor additions such as Cr, Al, Ni, etc. The steels thus developed were characterized using FE-SEM, XRD, microhardness tester, universal testing machine (UTM) and 3-dimensional Atom Probe Tomography (APT). The alloy steels after casting and homogenization were subjected to hot rolling at 1100 °C, with rolling exit temperature 900 ± 50 °C. The FE-SEM micrographs in SE mode revealed a complex phase microstructure with martensite, ferrite, bainitic ferrite and retained austenite in the specimens obtained after rolling and air cooling. The microhardness of the developed alloys is found in the range of 395–502 VHN in the hot-rolled and air cooled condition of the specimen. The tensile strength of alloys was measured to be in the range of 1412–1614 MPa with elongation of 12.12 %–18.92 %. The analysis of fracture surfaces after tensile tests for developed alloys revealed that Alloy 1 (Fe-4Mn-1.5Si) had dimples indicating ductile fracture while Alloy 2 (Fe-6Mn-1.5Si) has a mixture of dimples and facets, and Alloy 3 (Fe-8Mn-1.5Si) has lower dimples but larger facets, confirming quasi-ductile fracture with a lower ductility limit of 12.12 %. Atom Probe Tomography was performed to study the complex phase structure at nanoscale through re-distribution of carbon and other alloying elements. 3D APT revealed the presence of very fine retained austenite film of thickness ∼4–5 nm and carbon content of 6–8 at.%. This complex phase microstructure obtained after hot rolling and normalizing is made of very fine bainitic ferrite with film type retained austenite providing TRIP effect, in addition martensite and ferrite resulting in high strength.

Optical and Mechanical Properties of the Multi-Transition Zones of a Translucent Zirconia.

To characterize the composition, flexure resistance, and optical properties of a multilayer translucent zirconia in relation to its multi-transition zones. A multilayer zirconia (5Y/4Y) and a conventional 3 mol% yttria partially stabilized zirconia (3Y) were investigated. Bar-shaped specimens were obtained from the enamel and dentin layers, and the vertical cross-section of 5Y/4Y (N = 10). A four-point flexural (σf) test was performed using a universal testing machine (1.0 mm/min). Plate-shaped specimens (N = 6) were also produced from the enamel, transition 1, transition 2, and dentin layers. Translucency parameters (TPab and TP00) were determined using a dental spectrophotometer (N = 6). X-ray fluorescence and X-ray diffraction techniques were used to analyze elemental (N = 2) and phase compositions (N = 2), respectively. Data were analyzed using analysis of variance (ANOVA) and Tukey's test (α = 0.05). The yttrium content and σf varied between layers of 5Y/4Y. 3Y had the highest σf, followed by dentin. Enamel and cross-section showed lower and statically similar σf. 3Y and dentin groups had similar but statistically lower TPab and TP00 than the enamel. Different layers of multilayered zirconia have distinct compositions, which affect their mechanical and optical properties. The weak enamel layer compromises the mechanical properties of cross-sectional specimens. The development of novel cubic-containing multilayer zirconia ceramics to produce monolithic restorations brings new challenges to dental clinicians and laboratory technicians. The CAD/CAM design of multilayered 5Y/4Y restorations should consider the esthetic and mechanical requirements of each clinical case, as different properties are found in the different layers of these materials.

Design and Development of Miniature Measuring Instrument for Parachute Cords Dynamic Load for Stepless Parachute Opening.

Spacecraft recovery technology is crucial in the field of aerospace, in which the parachute plays a key role in slowing down the descent speed of the spacecraft and realizing a smooth landing. In order to construct a dynamically adjustable parachute deployment strategy, it is necessary to measure the parachute dynamic load accurately in real-time. However, the existing sensor measurement scheme makes it difficult to meet the measurement requirements due to its large structure and complex wiring. In order to meet the current demand for real-time measurement of parachute cords dynamic load, a miniature measuring instrument is designed. According to the function and technical requirements of the miniature measuring instrument, the hardware modules of the acquisition system are selected and designed, and the integration debugging and performance optimization of the microcontroller module, A/D sampling module, signal acquisition circuit, and power supply module are carried out. The software of the parachute cords tension acquisition system based on the miniature measuring instrument is developed. The Load Cell is modeled by using SolidWorks 2022 and statically analyzed by using Ansys 2022 R1 Workbench finite element analysis software. Then the final structure of the Load Cell and the pasting position of the strain gauge are determined through the results analysis as well as experimental verification. The hardware module of the signal acquisition system for the miniature measuring instrument is then encapsulated. The force value of the miniature measuring instrument is calibrated and tested many times by using the microcomputer-controlled electronic universal testing machine. The experimental results show that the designed miniature measuring instrument has accurate data, strong stability, and good real-time performance, which meets the demand for real-time accurate measurement of miniature measuring instruments, and can provide reliable data for parachute cords parameter validation and stepless unfolding design.

A Comparison of the Shear Bond Strength between a Luting Composite Resin and Both Machinable and Printable Ceramic–Glass Polymer Materials

This study aims to compare the shear bond strength (SBS) and Weibull characteristics between a luting composite resin and both printable and two different machinable ceramic–glass polymer materials. A total of 36 substrates were prepared, with 12 in each group. Printable substrates (12 mm × 12 mm × 2 mm) were printed by using permanent crown resin (3D-PR). Machinable substrates were obtained from Cerasmart 270 (CS) and Vita Enamic (VE) blocks (2 mm in thickness). The bonding surfaces of substrates were polished and airborne abraded (50 µm Al2O3). A self-adhesive luting composite resin (RelyX U200, 3M ESPE, St. Paul, MN, USA, SLC) was applied on substrates with the help of a cylindrical (Ø3 × 3 mm) mold. The SBS test was conducted using a universal test machine. The SBSs of three materials were compared using a one-way analysis of variance (ANOVA) (α = 0.05). The Weibull modulus was calculated for each material. The Kruskal–Wallis and chi-square tests were carried out for the failure mode analysis. There was no significant difference between the SBSs of the three materials (p = 0.129). The Weibull modulus was 3.76 for the 3D-PR, 4.22 for the CS, and 6.52 for the VE group. Statistical analysis showed no significant difference between the failure modes of the groups (p = 0.986). Mixed-failure fractures were predominantly observed in all three groups. The results show that the SBS of the SLC to printable 3D-PR is comparable to that of CS and VE material. Failure modes of printable 3D-PR show similar results with two different machinable ceramic–glass polymers.

Increasing the Interlayer Fracture Toughness of Polymer Fabric Composites Using Local 3D-Reinforcement (Felting)

Introduction. One of the reasons for undesirable delamination of polymer composites with fabric reinforcement is low transverse shear properties. It is known that the reinforcement of polymer fabric composites in the Z direction reduces the sensitivity to delamination and increases the viscosity of interlayer fracture. Various methods of three-dimensional reinforcement of polymer fabric composites are proposed in the literature. However, they complicate the manufacturing process of the structure. The problem is solved by the method of three-dimensional reinforcement proposed in this article — felting. This is a local reinforcement of the composite in the Z direction with minimal production changes. The degree of Z-reinforcement is determined by the felting density, i.e., the number of needle punches per 1 cm2 of the fabric package. The work is aimed at evaluating the effect of felting on the interlayer crack resistance of a composite material.Materials and Methods. The interlayer fracture toughness GIIc was determined on a cross-woven fiberglass with felting of 10 cm-2. The material was impregnated with Etal-370 resin and Etal-45 hardener. Experiments according to ASTM D7905M–14 and GOST 33685–2015 standards were carried out on an Instron 5900R test machine. The stress state at the crack tip was analyzed with regard to the nonlocal strength theory in the ANSYS Workbench program (option “static strength analysis”). The finite element method (FEM) was used.Results. The “load — displacement” curves were considered for the samples. Values GIIc were calculated. The results of ENF tests for felting density of 0 cm–2 and 10 cm–2 were summarized. Control samples and felting samples were compared. In the latter case, GIIс turned out to be ~33% higher. The stress state at the crack tip was calculated under DCB and ENF loading. The dependences of maximum normal and shear stresses, as well as displacements, were visualized in the form of graphs and color charts. To get the calculated “load — displacement” dependences using FEM, the reverse method of obtaining transverse shear constants was used. DCB loading showed that felting provided increasing the rupture strength in the Z direction to ~18%, by 39 to 46 MPa, and in the planes XZ— to ~16%, by 77 to 89 MPa.Discussion and Conclusion. Felting as a method of local three-dimensional reinforcement enhances the interlayer crack resistance of polymer fabric composites. It provides reducing the area of stratifications after local impacts during the operation of structures. Flexible felting technology makes it possible to create zones with an arbitrary impact density, increasing fracture toughness only in the required places of structures. The FEM analysis of the stress state at the crack tip within the framework of the nonlocal strength theory has shown that in strength calculations, the stratification crack can be considered as a stress concentrator.

Medial open wedge osteotomy yields comparable stability to lateral open wedge procedure on the distal femur.

Supracondylar osteotomies are a frequently and successfully used technique in the treatment of coronal plane deformities and unicompartmental osteoarthritis of the knee. While lateral open wedge techniques are common for valgus deformities, the data about medial open wedge techniques for varus deformities is sparse. The aim of this study was to compare the biomechanical properties of medial and lateral open wedge osteotomies using a locking Tomofix® plate (DePuy Synthes, Oberdorf, Switzerland). Our hypothesis was that there would be no difference regarding biomechanical outcome parameters between these two groups. Medial and lateral open wedge osteotomies were performed in composite bone model as routine. Each experimental group contained 6 constructs. Standardized osteotomy gaps of ten millimeters were performed and Tomofix® plates were fixed to third generation composite bones. The constructs were subsequently mounted into a servohydraulic testing machine. Axial and torsional loadings were applied as described in previous experimental studies. All specimens were subject to a load to failure mode with the mechanism of failure being noted. Both experimental groups showed comparable biomechanical properties under axial and torsional loadings. Mean high force axial stiffness was 3772 N/mm for lateral and 4185 N/mm for the medial construct. Significant differences were noted for torsional stiffness under low- (0 N) and mid-force (150 N) loadings (P = 0.002; P = 0.009), favoring the medial open wedge constructs. Medial open wedge osteotomy yields comparable biomechanical stability to the lateral open wedge procedure on the distal femur in a composite bone model.

Use and feasibility of a Lynch Syndrome predictive model for inherited colorectal and endometrial cancer in a low-middle income country.

While universal tumor testing for Lynch Syndrome (LS) is recommended in all new diagnoses of colorectal cancer (CC) and endometrial cancer (EC), the cost and availability of this test in low-resource settings poses challenges. The PREdiction Model for gene Mutations (PREMM5) is a clinical algorithm designed to assess the risk of an individual carrying estimates one's risk of carrying a LS mutation. This study aims to assess the feasibility of using PREMM5 to screen for LS risk in Guatemala. This cross-sectional pilot study enrolled 50 patients with colorectal or endometrial cancer receiving treatment at LIGA-INCAN, a cancer hospital in Guatemala City, between June 2022-July 2022. Patients were contacted by phone and administered the PREMM5 survey, followed by an additional feasibility questionnaire. Of the 50 participants, 62% of patients had a PREMM5 predicted probability of ≥ 2.5%, the threshold above which genetic testing is recommended. Almost all patients found the survey easy to complete (98%), were able to easily recall personal (90%) and family (88%) medical history, understood its purpose (94%), and reported an interest in (96%) and ability to (98%) act on the results if applicable. Our study shows the role of the PREMM5 as a feasible tool for identifying individuals at risk of carrying mutations associated with LS in this low-resource setting. By implementing the PREMM5 model, high risk individuals can be identified early, enabling timely interventions and improving outcomes in this at-risk population.

Analysis, modelling, and optimization of force in ultra-precision hard turning of cold work hardened steel using the CBN tool

The machinability of high-performance materials such as superalloys, composites, and hardened steel has been a big challenge due to their mechanical, physical, and chemical properties, which give them inherent complex machining characteristics. Additionally, majority of machinability tests conducted on these materials have been carried out on conventional and less precise lathes based on Taguchi, composite, and other designs of experiments that do not exploit all the possible combinations of cutting parameters. This work reports an investigation on ultra-precision hard turning (UHT) of cold work hardened AISI D2 steel of HRC 62, based on the full factorial design of experiment, carried out on an ultra-precision lathe. A theoretical analysis of the force components generated is reported. Modelling of the process, based on the resultant force, is also reported through a machine learning model. The model was developed from the experimental data and statistically evaluated with validation data. Its average MAPE values of 1.47%, 4.81%, and 10.66% for training, testing, and validation, respectively, attest to its robustness. The excellent coefficient of determination values, R2, also justify the model’s robustness. Multi-objective optimization was also conducted to optimize material removal rate (MRR), resultant force, and vibration simultaneously. For sustainable and efficient UHT, optimal cutting velocity (158.8 m/min), feed (0.125 mm/rev), and depth of cut (0.074 mm) were proposed to generate optimal resultant force (224.8 N), MRR (2603.6 mm3/min), and vibration (0.03 m/s^2) simultaneously. These results can be beneficial in planning UHT processes for high-performance materials.

An In Vitro Evaluation of Mechanical Properties of a New Dual-cure, Universal, Bioactive Luting Cement.

The aim of this study was to determine the properties of a new luting cement, BioCem®, by evaluating shear bond strength (SBS) and flexural strength (FS). A total of 60 extracted deciduous molars were included in this study. Samples were divided into two groups: Group I, Fuji I® (n = 30), and group II, BioCem® (n = 30). Each tooth was embedded in one acrylic block, such that the flattened enamel surface was exposed. Cylinders of 6 mm diameter and 8 mm height were prepared and evaluated for SBS using a universal testing machine. Ten rods of 25 × 2 × 2 mm of each material were prepared using a custom mold to evaluate the FS using a universal testing machine. Statistical Package for the Social Sciences (SPSS) version 20.0 was used for statistical analyses. Intergroup analysis was performed using an independent sample t-test. Upon comparing the SBS values of the luting agents and prepared enamel surfaces, glass ionomer cement (GIC) displayed the highest value, while BioCem® displayed the lowest. Upon comparing the FS values of the luting agents and prepared enamel surfaces, BioCem® performed better than GIC. BioCem® may be used as a luting agent for the cementation of stainless steel crowns (SSCs) on primary teeth. BioCem®, a recently developed luting cement, may be used for cementing SSCs to the surfaces of prepared deciduous teeth; it exhibits significantly higher FS but lower SBS than that of GIC. Shams SA, Nekkanti S, Shetty S. An In Vitro Evaluation of Mechanical Properties of a New Dual-cure, Universal, Bioactive Luting Cement. Int J Clin Pediatr Dent 2024;17(8):887-891.

Evaluation of the Bond Strength of Acrylic Teeth to Denture Base after Various Chemical Surface Treatments: An In Vitro Study.

The purpose of the present study was to assess the bonding capacity and efficacy of acrylic teeth to denture bases following two different chemical surface treatments. A two-metal mold measuring 35 mm in length and 12 mm in diameter was created specifically for the investigation in order to standardize the wax pattern-based tooth attachment at 45°. Following standard protocol, 75 wax cylinder specimens were flasked, dewaxed, and surface treatment of teeth was done as follows with 25 samples in each group-group I: control group, group II: monomethyl methacrylate monomer group, group III: acetone group. The curing process was completed following the packing of the denture base material. The samples' shear bond strength was assessed using a universal testing machine. Every sample was taken out when it fractured, and the shear load (Newton, N) was noted. The significance of the variation in applied shear load was assessed using one-way analysis of variance (ANOVA) and post hoc ANOVA Tukey's honestly significant difference (HSD) test at the 5% level of significance. The maximum shear bond strength was found in the samples treated with acetone (183.21 ± 0.06) followed by samples treated with monomethyl methacrylate monomer (171.64 ± 0.12) and the control group (149.32 ± 0.04). A statistically significant difference was found between the different groups (p < 0.001). In conclusion, according to the current study's findings, acetone chemical surface treatment of acrylic teeth produced the strongest bond when compared with the control group and monomethyl methacrylate monomer. In prosthodontic practice, artificial teeth regularly de-bond and separate from the denture base. A weak interface is produced when certain clinical conditions, such as ridge prominence, cause excessive cutting of the acrylic teeth and base. Where the denture base polymer meets the teeth's highly cross-linked matrix, it de-bonds adhesively. Therefore, the bonding between the acrylic teeth and the denture base material can be improved by the chemical surface treatment. How to cite this article: Chaudhuri NG, Lahiri B, Francis NT, et al. Evaluation of the Bond Strength of Acrylic Teeth to Denture Base after Various Chemical Surface Treatments: An In Vitro Study. J Contemp Dent Pract 2024;25(6):514-517.

Process parameter interaction study for mechanical strength of r-HDPE filled calcium carbonate composites

Abstract The increasing issue of plastic waste disposal has drawn attention to the urgent requirement for sustainable solutions. At the heart of this problem is polyethylene, a crucial industrial resin that has significant implications for recycling. This study aims to explore the feasibility of using recycled high-density polyethylene (rHDPE) derived from waste carpet as a sustainable alternative material for structural applications that undergo mechanical loads. The primary focus of this research is to incorporate calcium carbonate an easily obtainable and cost-effective inorganic mineral filler into the rHDPE. This will enhance mechanical strength. Calcium carbonate (CaCO3) is widely recognized for their reinforcing properties in various polymer composites, and in addition not only improves the mechanical strength of the blend but also reduces the environmental impact associated with plastic and waste carpet disposal. Our experimental approach involves preparing samples with varying compositions of rHDPE and calcium carbonate. This includes carefully considering extrusion process parameters such as screw speed and melting temperature. Mechanical testing was performed using a universal testing machine following the ASTM standard. The findings of this research are expected to open up new avenues for innovative strategies in reducing plastic waste and promoting the sustainable utilization of waste carpets thereby contributing to the broader field of environmental sustainability

Cellulose Fiber with Enhanced Mechanical Properties: The Role of Co-Solvents in Gel-like NMMO System.

Cellulose has garnered attention in the textile industry, but it exhibits limitations in applications that require high strength and modulus. In this study, regenerated cellulose fiber with enhanced mechanical properties was fabricated from a gel-like N-methylmorpholine N-oxide (NMMO)-cellulose solution by modulating the intermolecular interaction and conformation of the cellulose chains. To control the interaction, two types of co-solvents (dimethyl acetamide (DMAc) and dimethyl formamide (DMF)) were added to the cellulose solutions at varying concentrations (10, 20, and 30 wt%). Rheological analysis showed that the co-solvents reduced the solution viscosity by weakening intermolecular interactions. The calculated distance parameter (Ra) in Hansen space confirmed that the co-solvent disrupted intermolecular hydrogen bonding within cellulose chains. The solutions were spun into fiber via a simple wet spinning process and were characterized by X-ray diffraction (XRD) and universal testing machine (UTM). The addition of co-solvent led to an increased crystallinity index (C.I.) owing to the extended cellulose chains. The modulus of the resulting fiber was increased when the co-solvent concentration was 10 wt%, regardless of the co-solvent type. This study demonstrates the potential for enhancing the mechanical properties of cellulose-based products by modulating the conformation and interaction of cellulose chains through the addition of co-solvent.